HBV infection is a serious health problem in Southeast Asia and Africa. Due to the increasing numbers of global travelling, HBV infection is no longer a regional disease. Vaccines which are available to the public contain only the small surface antigen of the virus and are proven to be 80 to 90% effective. The presence of the PreS1 and PreS2 in the large antigen might elicit an immune response in non-responders of the vaccines of small antigen. Numerous lines of clinical and experimental evidence have been accumulating which implicate the PreS domains in the infectious cycle of HBV by directly participating in the interaction of virus with host cells. The objective of the project is to prepare the PreS1 fragment of the surface antigen and the large surface antigen (preS1+preS2 and small antigen) by recombinant DNA technology. The preS1 peptide and the large surface antigen will be used to assess their binding activities to membranes of human hepatocytes and their possible clinical use will be explored.